Today, we learn why you don't have to put
mayonnaise in the refrigerator. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
created them.

Years ago, in the army, I'd
argue with friends in the mess hall. We wanted our
coffee to be as warm as possible when we got around
to drinking it. Should we put the cream in right
away or should we wait. The question was loaded
with possibilities.

After all, the cream warms while the coffee cools.
Coffee loses heat fastest when it's hottest, before
we put cream in. Convection's less effective in
creamy liquid -- and so on and on.

To this day I don't know the answer. But, when I
left the army I went off to do a Ph.D. in thermal
science. Questions -- even seemingly silly
questions -- do open doors.

Now I turn pages in a neat little book on rainbows,
curve balls and other wonders of the natural world
by Ira Flatow. And those long formative
conversations come back to me.

Flatow gazes at the colorful multidimensional world
around us. He asks us to join in asking how it
works. He doesn't organize his questions by
scientific field. Instead, he takes us where you
and I might really go -- to the beach, the kitchen,
the concert hall, the ball park, the bathroom.

That makes his questions plausible. They're
questions you might ask -- not ones a scientist
would want you to ask.

We walk through the kitchen. We ask about air
bubbles lining a water glass that's been left
standing. We ask about boiling water -- about the
sounds it makes -- about why watched pots don't
boil. That's my field, and he's got it right. Maybe
he read the book I wrote long after I left that
army mess hall.

You see, the processes on your kitchen stove are
like the ones in a modern power plant. The mind
that questions things around it is the same mind
that reshapes things around it. Lessons lurk in
questions about microwave ovens, breaking eggs, and
cooking meat.

At the beach we ask why waves break and the sky is
blue, why rainbows are arcs of a circle. At the
ballpark we ask if pitchers really can throw curve
balls and why bats have a sweet spot.

I recognize so many of Flatow's questions. They're
the same questions that shaped me -- that made me
an engineer. They're the questions that'll make
your sons and daughters into engineers and chemists
-- into artists and mechanics.

Oh yes: Why don't you have to put mayonnaise in the
refrigerator? It's because it has vinegar in it.
The high acidity kills germs. But, if you make
mayonnaise into a salad dressing, you dilute it.
Then it's vulnerable to contamination.

So don't leave that salad dressing out.

I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.

(Theme music)

Flatow, I., RAINBOWS, CURVE BALLS, and Other
Wonders of the Natural World Explained. New
York: William Morrow and Company, Inc., 1988.

Be careful with your mayonnaise, by the way. It may
not grow bacteria outside the refrigerator, but it
can go bad without becoming toxic in not too many
days. I keep mine in the refrigerator.